Abstract
The biological relevance of extracellular vesicles (EV) in intercellular communication has been well established. Thus far, proteins and RNA were described as main cargo. Here, we show that EV released from human bone marrow derived mesenchymal stromal cells (BM-hMSC) also carry high-molecular DNA in addition. Extensive EV characterization revealed this DNA mainly associated with the outer EV membrane and to a smaller degree also inside the EV. Our EV purification protocol secured that DNA is not derived from apoptotic or necrotic cells. To analyze the relevance of EV-associated DNA we lentivirally transduced Arabidopsis thaliana-DNA (A.t.-DNA) as indicator into BM-hMSC and generated EV. Using quantitative polymerase chain reaction (qPCR) techniques we detected high copy numbers of A.t.-DNA in EV. In recipient hMSC incubated with tagged EV for two weeks we identified A.t.-DNA transferred to recipient cells. Investigation of recipient cell DNA using quantitative PCR and verification of PCR-products by sequencing suggested stable integration of A.t.-DNA. In conclusion, for the first time our proof-of-principle experiments point to horizontal DNA transfer into recipient cells via EV. Based on our results we assume that eukaryotic cells are able to exchange genetic information in form of DNA extending the known cargo of EV by genomic DNA. This mechanism might be of relevance in cancer but also during cell evolution and development.
Highlights
Mesenchymal stromal cells (MSC) have emerged as promising therapeutic tool for tissue regeneration
Thery et al described exosomal proteins implicated in apoptosis, e.g. histones released as complexes with DNA by cells undergoing apoptosis [31]
Our data suggest that the detected DNA is not derived from apoptotic or necrotic cells, since (i) we monitored high cell survival rates during all experiments of >97%; (ii) several centrifugation steps removed necrotic cells and apoptotic bodies; (iii) no fragmented DNA typical for apoptosis was detected in agarose gel electrophoresis and bioanalyzer even in extracellular vesicles (EV) derived from cell cultures with high number of dead cells; (iv) DNA is not co-sedimented by ultracentrifugation; and (v) DNA was not organized in nucleosomes
Summary
Mesenchymal stromal cells (MSC) have emerged as promising therapeutic tool for tissue regeneration. Secretion of bioactive molecules is believed to be the main mechanism by which MSC achieve their therapeutic effect [1]. As suggested by studies in man and rodents, MSC provide trophic signals that inhibit apoptosis and fibrosis and stimulate angiogenesis and mitogenesis [2,3,4]. Administered MSC did not home to the injured tissues but were. DNA Transfer with Extracellular Vesicles trapped in the lungs after i.v. injection without long term survival [5]. MSC showed the full range of protective properties. How do MSC transfer their protective potential to the side of need?
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